bug in logarithm()
Jeff Johnston
jjohnstn@redhat.com
Wed Oct 17 20:16:00 GMT 2007
Patrick Mansfield wrote:
> On Wed, Oct 17, 2007 at 12:28:47PM +0200, Martin Koeppe wrote:
>
>> Hi again,
>>
>> I'm using newlib on a i386 architecture, and now I wonder if it's
>> possible to configure libm in such a way that the fast asm versions of
>> e.g. log() are used. In my current newlib-libm.a there are the entry
>> points for _f_log() etc., but apparently log() doesn't make use of
>> _f_log().
>>
>> (How) Is it possible to configure newlib's libm to make use of _f_log
>> within log()?
>>
>> Thank you very much
>>
>
> They aren't compatible per comments in the code. You could call them
> directly. AFAIUI there should be prototypes and proper names (without
> underscore prefix, like #define f_log _f_log) for them in newlib, but I
> don't see any.
>
> -- Patrick Mansfield
>
Actually, they are meant to be called when the user specifies
-ffast-math on the compilation.
The definitions used to be part of libc/include/machine/fastmath.h with
an i386 check. This got inadvertently left out when we initially made
the transition of newlib from internal to external repositories.
Anyway, I have added libc/machine/i386/machine/fastmath.h based on the
older sources plus a few changes. If you compile your code with the
-ffast-math option, <math.h> will bring in <machine/fastmath.h> and you
will get access to the few fast math routines available for x86,
including log().
-- Jeff J.
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